1. Field of the Invention:
This invention relates to a method for the production of fluorinated quinones. More particularly, this invention relates to a method for the production of fluorinated quinones by the halogen exchange reaction of chlorinated aromatic compounds with a fluorinating agent.
2. Description of the Prior Art:
The so-called halogen exchange reaction, namely the exchange of fluorine and other halogen atoms by the reaction of an alkali fluoride upon aromatic halides has long been known to the art. Generally, such halogen exchange reactions are carried out mainly in such aprotic polar solvents as dimethyl sulfoxide (DMSO), sulfolane (TMSO .sub.2), N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), and dimethyl sulfone (DMSO .sub.2) at temperatures below the boiling points of these solvents [e.g. Ishikawa: Journal of organic Synthetic Chemical Society, Japan, Vol. 25, Page 808 (1967), and M. Hudlicky, Chemistry of Organic Fluorine Compounds, page 112 (1976), John Wiley & Sons Press]. Some cases have been reported in which phase transfer catalysts such as crown compounds were added for the purpose of expediting reactions involved.
The solvents generally used in halogen exchange reactions are such that when reaction temperatures are elevated for improving yields or when the solvents themselves are used for a long time, the solvents undergo decomposition or react with raw materials or reaction products to give rise to by-products and eventually impair yields. Further, these solvents have the disadvantage that they are not so easily recovered or reclaimed as to render their commercial use feasible. To avoid the drawback that these solvents are not effectively used at elevated temperatures, the practice of carrying out the halogen exchange reactions at elevated temperatures ranging from 190.degree. to 500.degree. C. in an autoclave without use of a solvent has found popular acceptance.
Separately methods for synthesizing fluorinated quinones from chlorinated quinones have been known to the art. A case is published in G. G. Yakobson et al.: Tr. Zhur. Ohschch. Khim., Vol. 36, page 142 (1966) in which 2,3-difluoro-1,4-naphthoquinone was synthesized by the halogen exchange reaction from 2,3-dichloro-1,4-naphthoquinone at 190.degree. to 195.degree. C. in an autoclave without use of a solvent.
In K. Wallenfels et al.: Chem. Ber., Vol. 90, page 2819 (1957), a case is published in which 1,2,3,4-tetrafluoroanthraquinone was synthesized by the halogen exchange reaction from 1,2,3,4-tetrachloroanthraquinone at 220.degree. to 250.degree. C. in an autoclave without use of a solvent.
It is safely inferred that since these methods invariably avoid using a solvent, the reactions generate heat and, therefore, the reaction systems offer the problem of difficult temperature control, and a large amount of carbonized materials remains fast to the vessel, rendering the methods themselves hardly feasible from the commercial point of view.
Methods for synthesizing octafluoroanthraquinone from tetrachlorophthalic anhydride have also been known to the art. One of such methods is disclosed in G. G. Yakobson et al.: Tetrahedron Letters, page 4473 (1965), for example. This method consists in heating tetrachlorophthalic anhydride at a temperature of 300.degree. C. in an autoclave in the absence of a solvent thereby subjecting the anhydride to both decarboxylation and halogen exchange and giving birth to octafluoroanthraquinone.
This method does not give the product in a satisfactorily high yield. Further, since this method uses no solvent, the reaction generates heat and, therefore, the reaction system offers the problem of difficult temperature control, and the reaction vessel suffers from heavy deposition of carbonized materials, rendering the method itself infeasible from the commercial point of view.
An object of this invention, therefore, is to provide a novel method for the production of fluorinated
Another object of this invention is to provide a method for the production of fluorinated quinones in a high yield by the halogen exchange reaction of chlorinated aromatic compounds with a fluorinating agent.